1. Field of the Invention
The present invention relates to an interleaf sheet for planographic printing plates, an abutting member for planographic printing plates, and a packaging structure for planographic printing plates.
2. Description of the Related Art
In recent years, planographic printing plates such as photosensitive printing plates and thermosensitive printing plates have been widely used in plate-making methods (including electrophotographic plate-making methods) in order to facilitate automation of plate-making processes. Planographic printing plates are generally manufactured in the following manner. On a support such as a sheet-configured or coiled aluminum plate, surface treatments such as graining, anodizing, a silicate treatment, and other chemical conversion treatments are carried out alone or in appropriate combination. Subsequently, processings for applying a photosensitive layer or a thermosensitive layer onto the support and drying the layer are carried out. (Hereinafter, these layers will be collectively referred to as xe2x80x9capplied filmsxe2x80x9d, and surfaces of supports with and without an applied film formed thereon are referred to as an xe2x80x9cimage forming surfacexe2x80x9d and a xe2x80x9cnon-image forming surfacexe2x80x9d, respectively.) Then, the support with the layer applied thereon is cut into a desired size.
The planographic printing plate manufactured in this manner is subjected to plate-making processings such as exposure, development, gum coating, and the like. Subsequently, the planographic printing plate is set in a printing machine, and ink is applied onto the planographic printing plate, thereby printing characters, images, or the like on papers.
In order to protect the applied film of a planographic printing plate, sometimes a sheet of paper called an xe2x80x9cinterleaf sheetxe2x80x9d is made to contact the image forming surface (i.e., the applied film). Particularly, in order to efficiently handle planographic printing plates, a plurality of planographic printing plates may sometimes be stacked in a thickness direction to form a stacked sheaf. In this case, the image forming surface (i.e., the applied film) is often protected by forming a stacked sheaf by, for example, alternatingly stacking the interleaf sheet described above and the planographic printing plate so that the interleaf sheet contacts the image forming surface, and by placing a protective cardboard on an end surface of the planographic printing plate in a stacking direction or placing it on every predetermined number of planographic printing plates.
However, in such a stacked sheaf, when a coefficient of static friction between the image forming surface of the planographic printing plate and the interleaf sheet or a coefficient of static friction between the interleaf sheet and the protective cardboard is small, the stacked sheaf may become disordered due to vibration or the like during transportation or the like of the stacked sheaf, or the interleaf sheet or the protective cardboard may be horizontally displaced relative to the planographic printing plate (i.e., displacement along the image forming surface of the planographic printing plate), thereby causing damage to the image forming surface.
Further, recently used are planographic printing plates of a photosensitive or thermosensitive type on which an image is formed with a laser (hereinafter referred to as a xe2x80x9claser exposure typexe2x80x9d). With such laser exposure type planographic printing plates, when the protective cardboard described above is used to form a stacked sheaf, depending on the characteristics of the planographic printing plate, moisture contained in the protective cardboard may cause the applied film to deteriorate. For this reason, a protective cardboard having a moisture-proofing layer may be used as needed. Often used is a structure in which a layer of low density polyethylene (LDPE) serving as the moisture-proofing layer is adhered to a generally used protective cardboard.
However, when the stacked sheaf which is formed by using such a protective cardboard with the LDPE layer adhered thereon is handled, since the coefficient of static friction between the LDPE layer and the interleaf sheet is large relative to the coefficient of static friction between the interleaf sheet and the image forming surface of the planographic printing plate, the interleaf sheet and the protective cardboard are together displaced horizontally relative to the planographic printing plate by vibration or the like during handling. The image forming surface may be subject to damage due to this horizontal displacement.
In view of the above-described facts, it is an object of the present invention to obtain an interleaf sheet for planographic printing plates, an abutting member for planographic printing plates, and a packaging structure for planographic printing plates which can prevent horizontal displacement of an interleaf sheet for a planographic printing plate relative to an image forming surface of a planographic printing plate and can reliably prevent damage to the image forming surface.
In accordance with a first aspect of the present invention, there is provided an interleaf sheet for planographic printing plates, comprising: a planographic printing plate contacting surface which contacts an image forming surface of a planographic printing plate with an applied film formed thereon in a state in which the planographic printing plate is packaged; and an abutting member contacting surface which contacts an abutting member for planographic printing plates which is disposed at a side that is opposite to a side of the planographic printing plate contacting surface, wherein surface properties of the planographic printing plate contacting surface and the abutting member contacting surface are respectively determined so that a coefficient of static friction between the abutting member for planographic printing plates and the abutting member contacting surface is no more than a coefficient of static friction between the planographic printing plate contacting surface and the image forming surface.
In other words, in the interleaf sheet for planographic printing plates according to the first aspect, in a state in which the planographic printing plate is packaged, the planographic printing plate contacting surface contacts and thereby protects the image forming surface (i.e., the applied film) of the planographic printing plate.
Further, by the abutting member for planographic printing plates being disposed on the surface opposite to the planographic printing plate contacting surface in a state in which the planographic printing plate is packaged, the abutting member for planographic printing plates is made to contact the abutting member contacting surface.
In the interleaf sheet for planographic printing plates according to the present invention, the surface properties of the planographic printing plate contacting surface and the abutting member contacting surface are set so that the coefficient of static friction between the abutting member for planographic printing plates and the abutting member contacting surface is equal to or less than the coefficient of static friction between the planographic printing plate contacting surface and the image forming surface. For this reason, for example, when horizontal displacement between the abutting member for planographic printing plates and the planographic printing plate is caused by external force, vibration, or the like during handling or the like, the interleaf sheet for planographic printing plates is not horizontally displaced relative to the planographic printing plate. Therefore, damage otherwise caused to the image forming surface by horizontal displacement of the interleaf sheet for planographic printing plates relative to the planographic printing plate can be reliably prevented.
In accordance with a second aspect of the present invention, there is provided an abutting member for planographic printing plates which, in a state in which an interleaf sheet for planographic printing plates is in contact with an image forming surface of a planographic printing plate with an applied film thereon, protects the planographic printing plate by contacting the surface of the interleaf sheet for planographic printing plates opposite to the surface which contacts the image forming surface of the planographic printing plate, the abutting member for planographic printing plates comprising: an interleaf sheet contacting surface whose properties are determined such that a coefficient of static friction between the interleaf sheet for planographic printing plates and the abutting member for planographic printing plates is no more than a coefficient of static friction between the image forming surface of the planographic printing plate and the interleaf sheet for planographic printing plates.
That is, the abutting member for planographic printing plates according to the second aspect contacts, of the surfaces of the interleaf sheet for planographic printing plates, the surface which is opposite to the surface in contact with the image forming surface of the planographic printing plate, and thereby protects the planographic printing plate.
The surface properties of the abutting member for planographic printing plates are set so that the coefficient of static friction between the interleaf sheet for planographic printing plates and the abutting member for planographic printing plates is equal to or less than the coefficient of static friction between the image forming surface of the planographic printing plate and the interleaf sheet for planographic printing plates. For this reason, for example, when horizontal displacement between the abutting member for planographic printing plates and the planographic printing plate is caused by external force, vibration, or the like during handling or the like, the interleaf sheet for planographic printing plates is not horizontally displaced relative to the planographic printing plate. Therefore, damage otherwise caused to the image forming surface by horizontal displacement of the interleaf sheet for planographic printing plates relative to the planographic printing plate can be reliably prevented.
In the abutting member for planographic printing plates according to the present invention, the interleaf sheet contacting surface is preferably formed by adhering an adhering member onto an abutting member main body which forms the abutting member for planograhic printing plates. The adhering member has, with respect to the interleaf sheet for planographic printing plates, a coefficient of static friction no more than a coefficient of static friction between the image forming surface and the interleaf sheet for planographic printing plates.
In other words, the adhering member has, with respect to the interleaf sheet for planographic printing plates, a coefficient of static friction which is equal to or less than the coefficient of static friction between the image forming surface of the planographic printing plate and the interleaf sheet for planographic printing plates. Accordingly, by merely disposing the abutting member for planographic printing plates with such an adhering member adhered thereon so that the adhering member contacts the interleaf sheet for planographic printing plates, horizontal displacement of the interleaf sheet for planographic printing plates relative to the planographic printing plate can be prevented. Further, since the adhering member is merely adhered onto a conventionally used abutting member for planographic printing plates, manufacturing cost is not increased.
The adhering member is not particularly limited as long as the surface properties thereof have the aforementioned coefficient of static friction with respect to the interleaf sheet for planographic printing plates. However, for example, the adhering member can be an adhering paper which has the same structure as that of the interleaf sheet for planographic printing plates which protects the image forming surface of the planographic printing plate. In this way, a new member need not be prepared for the adhering member, and generally used interleaf sheets for planographic printing plates can be used. Therefore, the abutting member for planographic printing plates can be manufactured at a lower cost. Further, in this case, for example, if the adhering paper is adhered onto the abutting member main body in such a manner that the surface of the adhering paper which has a relatively smaller coefficient of static friction with respect to the interleaf sheet for planographic printing plates contacts the interleaf sheet for planographic printing plates, the coefficient of static friction between the abutting member for planographic printing plates and the interleaf sheet for planographic printing plates is further decreased.
In accordance with a third aspect of the present invention, there is provided a packaging structure for planographic printing plates, comprising: a planographic printing plate; an interleaf sheet for planographic printing plates which is made to contact an image forming surface of the planographic printing plate with an applied film formed thereon; and a protecting member for planographic printing plates which protects the planographic printing plate by being made to contact a surface of the planographic printing plate opposite to the image forming surface, wherein a coefficient of static friction between the protecting member for planographic printing plates and the interleaf sheet for planographic printing plates is set so as to be no more than a coefficient of static friction between the planographic printing plate and the interleaf sheet for planographic printing plates.
That is, in this packaging structure for planographic printing plates, the image forming surface (i.e., the applied film) of the planographic printing plate is protected by contacting the interleaf sheet for planographic printing plates.
Moreover, the protecting member for planographic printing plates contacts the interleaf sheet for planographic printing plates at the surface thereof which is opposite to the surface in contact with the planographic printing plate. Therefore, deformation of the planographic printing plate or damage thereto is prevented.
The interleaf sheet for planographic printing plates and the protecting member for planographic printing plates are structured such that the coefficient of static friction between the protecting member for planographic printing plates and the interleaf sheet for planographic printing plates is equal to or less than the coefficient of static friction between the planographic printing plate and the interleaf sheet for planographic printing plates. For this reason, for example, when horizontal displacement between the protecting member for planographic printing plates and the planographic printing plate is caused by external force, vibration, or the like during handling or the like, the interleaf sheet for planographic printing plates is not horizontally displaced relative to the planographic printing plate. Therefore, damage otherwise caused to the image forming surface by horizontal displacement of the interleaf sheet for planographic printing plates relative to the planographic printing plate can be reliably prevented.
The protecting member for planographic printing plates is not particularly limited as long as it can prevent deformation of the planographic printing plate or damage thereto. For example, the aforementioned abutting member for planographic printing plates can be used as the protecting member for planographic printing plates.
In the packaging structure for planographic printing plates according to the present invention, the coefficient Y of static friction between the protecting member for planographic printing plates and the interleaf sheet for planographic printing plates, and the coefficient X of static friction between the planographic printing plate and the interleaf sheet for planographic printing plates are preferably 0.37 or more.
As described above, by the coefficient Y of static friction between the protecting member for planographic printing plates and the interleaf sheet for planographic printing plates, and the coefficient X of static friction between the planographic printing plate and the interleaf sheet for planographic printing plates being 0.37 or more, damage otherwise caused to the image forming surface of the planographic printing plate can be reliably prevented. Further, disorder of the packaging structure for planographic printing plates can also be prevented.